How to add non-class spells to my class?

In our game this past weekend the DM gave my Cleric a cantrip spell to use. One of our party is an undead Fighter, so the usual heal spells are actually harmful to him. He "heals" by drinking poison. So my character prayed to his deity to grant him the ability to heal this poor friend of his, and granted the use of Poison Spray. Obviously that's not in the usual toolbox of a Cleric, so how would I add this to the character in the Beyond, without having to do Homebrew?

In addition to the feat option another way to go about it is homebrew-copying the poison spray cantrip and just adding Cleric to its class availability.

I was hoping to not go the Homebrew path, but I guess it's ok, thanks for the help. 

Yeah, this is why I hesitate when Homebrewing. I made the spell, it says it's Private and Never Submitted, but I'm trying to add this to my character sheet. There's always some additional steps I can never remember, it's like having to operate on my own appendix up through my ....nose. Is there a pinned How To for Homebrewing that includes that portion of adding to the character?

Quote from izgerry >>

Yeah, this is why I hesitate when Homebrewing. I made the spell, it says it's Private and Never Submitted, but I'm trying to add this to my character sheet. There's always some additional steps I can never remember, it's like having to operate on my own appendix up through my ....nose. Is there a pinned How To for Homebrewing that includes that portion of adding to the character?

 Should be as simple as going to the first page of your character creation, enabling homebrew, and then adding it like you would anything else.

The Homebrew is enabled, yes. In previous characters where I wanted to add a weapon for example, I ran into the same problem. It wouldn't show in the inventory. I had to do...something...just can't remember what, so that I could see it on the character.